1. Field of the Invention
The present invention relates to a novel process for the production of isomaltulose (.alpha.-D-glucopyranoside-1,6-fructose). The starting material of the process, i.e., a combination of glucose and fructose, is preferably available, for example, as high fructose syrup (HFS). The product isomaltulose, per se, is used as a non cariogenic sweetener, and is also a starting material for the production of Palatinit (Suddeutsche Zucher AG) which is a low calory sweetener.
Note, Palatinit: an equimolecular mixture of isomers .alpha.-D-glucopyranoside -1,6- mannitol and .alpha.-D-glucopyranoside -1,6- glucitol.
2. Description of the Related Art
In known processes for the production of isomaltulose, sucrose is enzymatically converted to isomaltulose. Namely, Japanese Examined Pat. Publication (Kokoku) No. 57-10720 corresponding to DE Nos. 72-2217628, 73-2307251 and 73-2307299 describes a process for the production of isomaltulose by culturing a microorganism belonging to the genus Protaminobacter or Serratia in a sucrose aqueous solution. Japanese Examined Pat. Publication (Kokoku) No. 58-38156 corresponding to DE Nos. 77-2741197 and 78-2806216 discloses a process for the production of isomaltulose from sucrose by continuous fermentation using a microorganism belonging to the genus Protaminobacter. Japanese Examined Pat. Publication (Kokoku) No. 60-9797 corresponding to GB No. 79-7938563; Japanese Unexamined Pat. Publication (Kokai) No. 57-94298 corresponding to DE No. 80-3038219; Japanese Unexamined Pat. Publication (Kokai) No. 59-2695 corresponding to DE No. 82-3213107; and Japanese Unexamined Pat. Publication (Kokai) No. 61-249396 corresponding to DE Nos. 85-3515284 and 85-3528752 disclose processes for production of isomaltulose by placing immobilized microbial cells or an immobilized enzyme in contact with a sucrose aqueous solution.
All the processes described above rely on the conversion of the .alpha.-1,2 linkage in sucrose to an .alpha.-1,6 linkage, by an enzyme. Therefore, it is believed that an equilibrium of conversion between sucrose and isomaltulose, is in favor of a production of isomaltulose.
Conversely, it has been believed that a synthesis of isomaltulose from monosaccharides glucose and fructose is disadvantageous from the point of view of the reaction equilibrium, because the reaction forms an ether linkage. Therefore, a process for the production of isomaltulose from glucose and fructose has not been disclosed.
But, since a mixture of glucose and fructose is economically and commercially available as a form of HFS, a process for the production of isomaltulose from a mixture of glucose and fructose, such as HFS or invert sugar, would be commercially advantageous.
Note, "high fructose syrup" (HFS) means a mixture of sugars produced by partially isomerizing a glucose preparation and containing glucose and fructose as main sugar components.